A prior art ink-jet printer typically includes a printing cartridge or pen in which small droplets of ink are formed and ejected toward a printing medium. Such pens include printheads with orifice plates having very small orifices or nozzles through which the ink droplets are ejected. Adjacent to the orifices inside the printhead are ink chambers, where ink is stored prior to ejection. Ink is delivered to the ink chambers through ink channels. Each orifice and associated structure which defines the ink chamber and ink channel is commonly known as a firing element. A manifold in the pen connects the firing elements to an ink supply. The ink supply may be, for example, contained in a reservoir part of the pen.
Ejection of an ink droplet through an orifice may be accomplished by quickly heating a volume of ink within the adjacent ink chamber. The rapid expansion of ink vapor forces a drop of ink through the orifice. This process is called "firing." The ink in the chamber may be heated with a transducer such as a resistor that is aligned adjacent to the orifice. If the orifice is not properly aligned with the transducer, the print quality of the pen can be adversely affected.
The current construction of orifice plates and method of attaching the orifice plates to printhead dies are prone to result in printheads whose orifice pates are misaligned. FIGS. 1 is a cross-sectional view of a prior art mandrel 2. This mandrel has a metallic layer 4 deposited on a substrate 6. The metallic layer 4 is appropriately photolithographically patterned and etched to provide a molding surface for electroforming an orifice plate 8. Holes in the metallic layer 4 have surfaces that electroform orifices 10 in the orifice plate 8. The orifice plate 8 that is formed by using such a prior art mandrel 2 is substantially uniformly thick and has a substantially flat surface 12. During the manufacturing of a printhead (not shown), it is this surface 12 of the orifice plate 8 that is attached to a barrier layer on a printhead die (not shown).
To increase manufacturing productivity, many such orifice plates are formed as a single sheet on an appropriate mandrel. After being electroformed to a predetermined thickness, the orifice plates are singulated for attaching individually to a printhead die. A machine picks and places each orifice plate over a corresponding printhead die on a wafer containing many such dies. The wafer and attached orifice plates are put through a "stake and bake" process to cause the orifice plates to adhere to the printhead dies. After the "stake and bake" process, each printhead consisting of a printhead die and an orifice plate is singulated using dice sawing. Each complete pair of orifice plate and printhead die is then ready for attaching to a pen body to complete the fabrication of an ink-jet pen.
During the "stake and bake" process, pressure is applied to the orifice plate to hold it in place over the printhead die. This pressure has the tendency to cause the orifice plate to shift and as a result become misaligned. Another recurring problem is adhesion of the orifice plate to the printhead die. Delamination can occur from residual stresses.
It is therefore desirable to have an orifice plate that ameliorates the misalignment and delamination problems associated with prior art electroformed orifice plates.
EP 0641 659 discloses a means of attaching an orifice plate made of tape automated bonding (TAB) circuit or flexible circuit on a printhead die so that orifices on the orifice plate are aligned over transducers on the printhead die. The alignment is achieved by copper traces on the TAB or flexible circuit mating with correspondingly etched channels in a barrier layer on the printhead die. With such alignment, only rough alignment is required when attaching the orifice plate to the printhead die. As the two are brought into contact, they tend to lock in place.
Such an alignment method works for a flexible circuit orifice plate but cannot be easily and economically duplicated for metal orifice plates. Firstly, copper traces cannot be run on metal orifice plates. With prior art methods of electroforming metal orifice plates, it is impossible for similar traces to be created on the metal orifice plates.
There is also a difference between the manufacturing process of a pen with a flexible circuit orifice plate and one with a metal orifice plate. For the former, the flexible circuit orifice plate is attached only after the printhead die is attached to a pen body. At such a stage, if there is any pen failure due to misalignment of the flexible circuit orifice plate, the whole pen is discarded. For the case of a metal orifice plate, the orifice plate is attached to the printhead die before the combination is attached to a pen body. The combination can be tested before attaching to a pen body. Yield loss in the manufacturing of metal orifice plate pens is therefore lower, making manufacturing of such pens preferable to those with flexible circuit orifice plates.
It is therefore advantageous to be able to create an electroformed orifice plate that can be attached to a printhead die so that orifices on the orifice plate are aligned over transducers on the printhead die.